Meeting Abstract

30.6  Sunday, Jan. 5 11:00  Adaptive timing of life cycle stages in a temporally-flexible nomadic songbird. HAHN, TP*; SCHULTZ, EM; KELSEY, TR; MACDOUGALL-SHACKLETON, SA; CORNELIUS, JM; Univ. California Davis; Univ. California Davis; Nature Conservancy; Univ. Western Ontario; Univ. California Davis tphahn@ucdavis.edu

Appropriate timing of life cycle events in varying environments is fundamental to survival and reproductive success. Achieving this when food supply and other environmental conditions vary capriciously in space, time, or both presents special problems. We have been interested in the question of whether dealing effectively with such conditions depends on adaptively specialized timing mechanisms or is based on a common system shared by taxa occupying a wide range of environments. Our studies of crossbills – nomadic songbirds that display particularly flexible annual schedules – reveal elements of adaptive specialization to deal with unpredictable changes in food supply, such as loss of absolute reproductive refractoriness to long days and tonic activity of the septo-infundibular gonadotropin releasing hormone system in the brain, and features in common with more typical seasonal breeders, such as a regularly-scheduled annual plumage molt and a consistent seasonal reproductive hiatus in autumn. Crossbills appear to be variations on the seasonal breeder theme, rather than fundamentally different in the way they orchestrate their annual schedules.